[A-CG39] Biogeochemical cycles in Land Ecosystem

[ACG39-P01] Long-term warming effect on heterotrophic respiration in a beech forest on Mount Naeba

*Munemasa Teramoto¹, Naishen Liang¹, Masaaki Naramoto², Jiye Zeng¹, Zhao Xin¹, Hajime Tomimastu¹ (1.Center for Global Environmental Research, National Institute for Environmental Studies, 2.Faculty of Agriculture, Shizuoka University)

Keywords:soil organic carbon, global warming, heterotrophic respiration, chamber, Asian monsoon

Soil respiration is the second largest carbon flux in terrestrial ecosystems and the global soil respiration is estimated to be 98 GtC yr^-1. Soil respiration consists of root respiration and heterotrophic respiration (R_h), and R_h contributes more than half of the soil respiration. It is commonly observed that R_h exponentially increases with temperature. Therefore, a small increase of temperature can result in a remarkable enhancement of R_h, indicating that it is an important positive feedback factor to accelerate global warming under a warmer environment. However, the long-term warming effect on R_h is not well understood especially in the humid Asian monsoon region.

To examine the long-term response of R_h to global warming in Asian monsoon forests, we set a multi-channel automated chamber measurement system in a beech forest on Mount Naeba in July 2007. We prepared 10 trenched chambers (90 cm × 90 cm × 50 cm) to continuously measure R_h. Half of those trenched chambers were artificially warmed by infrared heaters 1.6 m above the soil surface (+2.5ºC), and the influence of soil warming on R_h was examined by comparing control plots and warming plots. Measurements were conducted mainly during growing season from June to October.

Even though there was a large inter-annual variation, enhancement of R_h by soil warming was confirmed in all 8 years measurements. Soil temperature was the primary factor for the seasonal variation of R_h. The influence of soil moisture on seasonal variation of R_h was relatively small.